Power failures may occur at cable joints in underground conduit networks. Some are due to partial discharges inside the joints and the corresponding degradation of their electrical insulation.
Diagnosis of underground cables and their accessories or equipment is desirable for safety issues, and for performing predictive maintenance and removing defective accessories or equipment before failure.
U.S. Pat. No. 6,809,523 (Ahmed et al.), U.S. Pat. No. 5,530,364 (Mashikian et al.), U.S. Pat. No. 5,767,684 (Steennis), U.S. Pat. No. 6,420,879 (Cooke), U.S. Pat. No. 6,507,181 (Pakonen et al.), U.S. Pat. No. 6,418,385 (Hücker et al.), U.S. Pat. No. 6,255,808 (Hücker), U.S. Pat. No. 6,297,645 (Eriksson et al.), U.S. Pat. No. 6,392,401 (Cooke), U.S. Pat. No. 5,642,038 (Kim et al.) and CA (Canadian) patent No. 2,455,206 (Wendel et al.) disclose certain methods and various devices for detecting partial discharges which are however not much reliable, imprecise, sensitive to noise, rudimentary, cumbersome, limited to some specific equipment to be tested, require that the equipment to be tested be out of service, or else difficult to be practically implemented due to manipulations requiring uncommon dexterity.
Partial discharges may also occur in a variety of electrical devices or equipment, and are often forerunners of more serious damages to follow if nothing is done to repair or replace the possibly defective equipment.